Escalating global threats from Russia to North Korea mean the U.S. military's regional commanders must update war plans to incorporate the use — in the most dire circumstances — of nuclear weapons, according to the Pentagon's latest Nuclear Posture Review.

The review responds to what President Donald Trump and military leaders say is an increasingly complex threat environment, and it acknowledges that prospects for further nuclear arms reductions in the near future are "extremely challenging." Military leaders see China and Russia in particular as bolstering their nuclear forces, incorporating them into their strategic plans and taking more aggressive actions in outer space and cyberspace.

The review is intended to "ensure that our diplomats and our negotiators are in a position to be listened to when we say we want to go forward on nonproliferation and arms control," Defense Secretary Jim Mattis told reporters Friday. "You do so by having an effective, safe deterrent — and you have to look at each of those words."